450 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



caution as a basis of establishing a parallel between rocks in 

 distant areas. 



Although Dumont's classification was based wholly upon 

 the characters displayed by the succession in Belgium, it is 

 nevertheless excellently arranged both stratigraphically and 

 lithologically. De Koninck and Murchison afterwards tried 

 to bring his classification into harmony with that of Great 

 Britain and the neighbouring districts of Germany. They 

 relegated the whole of the Terrain Ardennais as well as the 

 Gedinnien group into the Silurian system, and the Coblentzien, 

 Ahrien, Eifelien, and the lower part of the Condrusien, into the 

 Devonian system. Subsequently, Gosselet has carried out a 

 series of studies extending over thirty years on the Palaeozoic 

 deposits of Belgium and the Ardennes, and has elucidated the 

 palaeontological and stratigraphical relations of the area with 

 admirable care and accuracy. 



The Devonian deposits in Brittany and the lower Loire 

 district have been examined by Barrois and Oehlert, while 

 the richly fossiliferous neighbourhood of Cabrieres, near Mont- 

 pellier, has been the subject of several able palaeontological 

 monographs by Fournet, Koenen, Freeh, De Rouville, and 

 others. The Spanish Devonian deposits have been described 

 by Verneuil, Casiano da Prado, Schulz, and Barrois; while 

 the Devonian occurrences in the eastern Alps have been eluci- 

 dated by Hoernes, Benecke, and Freeh. 



D. Carboniferous System. Less difficulty is offered in the 

 classification of the Carboniferous system than in that of the 

 three oldest Palaeozoic systems of which Freeh has given an 

 exhaustive account in the Lethcea Palceozoica (1897). As far 

 back as 1808, D'Omalius d'Halloy comprised the Belgian Car- 

 boniferous limestone as a lower group, and the sandstones, 

 shales, and seams as an upper group under the name of 

 Terrain bituminifere or Houiller. In 1822 Conybeare and 

 Phillips included Carboniferous limestones, the millstone grit 

 and coal measures in the Carboniferous system, but they also 

 placed in it the Old Red Sandstone as a lower sub-division. 

 Murchison and Sedgwick in 1839 transferred the Old Red 

 Sandstone into the Devonian, and recognised in the so-called 

 Culm shales of Devonshire, and in the shales with Posidonomya 

 Becheri in Germany, an arenaceous and argillaceous littoral 

 equivalent of the Carboniferous limestone. The sub-division 



